F5 iControl LX - How to access additional error response data (lines 25 & 26)

Better_Error.js

/**
 * Apply the new, or modified, service definition to the BIG-IP
 * @param {Object} service_def retireved from GitHub repo
 * 
 * @returns {Object} AS3's declaration processing results
 */
MyWorker.prototype.applyServiceDefinition = function (service_def) {

  return new Promise((resolve, reject) => {

    // Build the declaration POST message
    var as3path = '/mgmt/shared/appsvcs/declare'; 
    var uri = this.restHelper.makeRestnodedUri(as3path);
    var restOp = this.createRestOperation(uri, service_def);
    
    // Send the declaration POST message to the BIG-IP
    this.restRequestSender.sendPost(restOp)
    .then((resp) => {

      resolve(resp.body.results);

    })
    .catch((err) => {

      let errorStatusCode = err.getResponseOperation().getStatusCode();
      let errorBody = JSON.stringify(err.getResponseOperation().getBody(), '', '\t');

      logger.info('[MyWorker - ERROR] - applyServiceDefinition(): ' +errorStatusCode+ ':\n' +errorBody);

    });

  });

};